Slickline cable, also referred to as wireline cable, can be used in a wellbore to provide downhole logging tool support and communication between the downhole environment and the surface of the well. The slickline cable can include communication cabling (e.g., fiber optics, metal conductor wires) between a wireline tool and the surface as well as the structural support to raise and lower the wireline logging tool.
Catastrophic failure of a composite material based slickline cable can be a result of continuous degradation of the cable mechanical strength, induced by a geological formation, and subsequent propagation of the various structural defects during downhole tool loading or service time. The wireline logging tool loading may produce either static tensile stress or transient tensile stress along the slickline cable. Specifically, the transient tensile stress event may lead to formation of various internal structural defects, such as cracking and delamination. Such structural defects may be localized and may not show obvious influence on cable performance at initial status. However, a percolation threshold can be trigged by continuous tensile stress loading. The initial nano-structural or micro-structural defects may grow along the loading axis, and propagate quickly, resulting in the slickline cable having non-uniform stress loading.
Existing nondestructive inspection technologies, such as laser ultrasonic, transient thermography, eddy current, or x-ray radiography, are useful during manufacture of the composite material based slickline cable but are difficult to be implemented in the downhole environment for real-time monitoring and diagnosis of potentially catastrophic slickline cable failures. In addition, these conventional nondestructive inspections are single-point analytical technique and difficult to effectively scan structural defects along full length of the slickline cable within limited time. There are resulting needs to detect slickline cable structural defects along full length of ˜30,000 ft in a downhole environment.